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Electric Formula.
and motor, the resistance of the circuit causing dissipation of
energy as heat. If
C = current in amperes, Q = quantity in Coulombs,
E — electromotive force in volts, W = work in foot pds.,
R = resistance in Ohms,
Then:
H.P =
c^j^
"746"
EC
746
746 R
v - R -'
EPR
v R E 746 H. P. /Hp-.-76-p w
*-i-
o w
C -VH.P.746R .73?Q 746 H. P. E2
C2 746 H. P.
If 7 be the length of a circuit in feet, both lead and return,
and a — sectional area of wire in sq. in.,
R at 60°
8-4
a 1,000,000
when copper wire is used. Also if the E. M. F. drops from E to
e and the current from C to c in flowing from generator to
motor, and if W is the work put in by generator and w that
received by motor,
Efficiency of circuit =-- = - = —-
Example 54.—A dynamo driven by turbine can generate 50
amperes at 300 volts. The current is carried by two Np. 6 W* G.
copper wires to drive a workshop motor \ mile away. Assuming the
commercial efficiency of the generator as 86%, and that of the motor
as 84°/0, find the mechanical efficiency of the whole system*